1. Field of the Invention
This invention relates to an electronic musical instrument, such as a synthesizer and an electronic piano, and more particularly to an electronic musical instrument adapted to vary a musical tone, which is produced based on a musical tone signal, depending on a note on/off velocity.
2. Prior Art
In electronic musical instruments, particularly those adapted to produce a musical tone in a manner correspondent to a selected key or keys of a keyboard thereof, such as a synthesizer, an electronic piano, an electronic organ, a single keyboard, and a tone generator module, it is a common technique to vary the musical tone in a manner responsive to the speed of depression of a key, i.e. the note on velocity. A conventional electronic musical instrument of this kind includes a plurality of waveform memories each storing data of musical tones, i.e. data of waveforms of musical tones, such as data of amplitudes and frequencies thereof, which are correspondent to a predetermined reference note on velocity peculiar thereto, and a plurality of respective readers associated therewith, which read data of a musical tone corresponding to pitch information obtained from a depressed key of the keyboard from the waveform memories associated therewith, respectively. Items of the data of the musical tone read by the readers from the waveform memories are mixed or added up to form a monaural tone signal. The tone color of the musical tone produced based on the tone signal is varied by changing the mixing ratio of the data of musical tone read from the respective waveform memories according to the note on velocity.
Therefore, the conventional electronic musical instrument must incorporate lots of waveform memories and tone data readers, which are expensive, to form a desired musical tone signal correspondent to the note on velocity, which results in increased manufacturing cost.